#include "test_string.h"
#include <algorithm>

char* add_str(char* dst, const char* src1, const char* src2)
{
    if (src1 == NULL || src2 == NULL || dst == NULL)
        return NULL;
    strcpy(dst, src1);
    strcpy(dst + strlen(src1), src2);

    return dst;
}

string add_string(string& s1, string& s2)
{
    return s1 + s2;
}

std::string to_upper(const std::string& input)
{
    std::string result = input;
    std::transform(result.begin(), result.end(), result.begin(),
        [](unsigned char c) { return std::toupper(c); });
    return result;
}